An electric powered vehicle such as an electric vehicle or a hybrid vehicle requires a high-voltage source for main machinery and a low-voltage source for auxiliaries. Conventionally, a DC/DC converter reduces a direct current (DC) voltage outputted from the high-voltage source for the main machinery to obtain a low voltage for the auxiliary.
Japanese Patent Laying-Open No. 7-170611 discloses an electric power control device for an electric vehicle, including such a DC/DC converter. The electric power control device includes a main battery, and a DC/DC converter that converts a high voltage from the main battery to a low voltage. In the electric power control device, the low voltage outputted from the DC/DC converter allows direct actuation of an electric load on a low voltage side.
This electric power control device has no battery for auxiliaries, and the DC/DC converter converts the high voltage from the main battery to the low voltage. Since the electric load on the low voltage side is directly actuated by the output from the DC/DC converter, the electric power control device is reduced in size and wiring in the electric power control device is performed readily.
The electric power control device disclosed in Japanese Patent Laying-Open No. 7-170611 is effective because the battery for the auxiliaries becomes unnecessary. However, the electric power control device still requires the DC/DC converter for converting the high voltage from the main battery to the low voltage.
Recently, in order to deal with an increase in electric loads to be mounted to a vehicle, a 42V power supply system tends to be used together with a conventional 14V power supply system. In future, it can be expected that various power supply systems will be mounted to one vehicle in accordance with loads to be mounted to the vehicle. However, provision of a DC/DC converter for each power supply system hinders size reduction, weight reduction, cost reduction and the like of a vehicle.